Method for producing pigments of improved dispersibility

ABSTRACT

Pigmentary metal oxides, e.g., titanium dioxide, are treated with an organic amine, e.g., triethanolamine, and an organic nitrogen compound containing an ionizable hydrogen atom attached to the nitrogen atom, the nitrogen atom being flanked by at least one carbonyl group, e.g., ortho-benzosulfimide.

nited States Patent Dietz 4 1 Mar. 21, 1972 METHOD FOR PRODUCINGPIGMENTS OF IMPROVED DISPERSIBILITY Inventor: Albert Dietz, NewMartinsville, W. Va.

Assignee: PPG Industries, Inc., Pittsburgh, Pa.

Filed: Aug. 7, 1970 Appl. No.: 62,161

Related US. Application Data Continuation-in-part of Ser. No. 849,894,Aug. 13, 1969, Pat. No. 3,549,396, which is a continuation-inpart ofSer. No. 506,608, Nov. 5, 1965, abandoned.

US. Cl ..l06/300, 106/288 B, 106/296, 106/297, 106/299, 106/300,106/304, 106/306, 106/308 N Int. Cl. ..C09c 1/00, C09c 1/36, C09c 3/00Field of Search ..106/288, 296, 297, 299, 300,

Primary Examiner-James E. Poer Attorney-Chisholm and Spencer [5 7]ABSTRACT Pigmentary metal oxides, e.g., titanium dioxide, are treatedwith an organic amine, e.g., triethanolamine, and an organic nitrogencompound containing an ionizable hydrogen atom attached to the nitrogenatom, the nitrogen atom being flanked by at least one carbonyl group, e.g., ortho-benzosulfimide.

9 Claims, N0 Drawings METHOD F OR PRODUCING PIGMENTS OF IMPROVEDDISPERSIBILITY C ROSS-REF ERENCE TO RELATED APPLICATIONS The presentapplication is a continuation-in-part application of my application,Ser. No. 849,894, filed Aug. 13, 1969, now U.S. Pat. No. 3,549,396,which was a continuation-inpart application of my application, Ser. No.506,608, filed Nov. 5, 1965, and now abandoned.

BACKGROUND OF THE INVENTION Pigmentary metal oxides, such as titaniumdioxide, iron oxide and silicon dioxide, have been treated with organiccompounds to improve their dispersibility and/or wetting properties insurface coating composition vehicles in which they are used. Usually,the improvement in wetting properties is selective to eitheroleoresinous vehicles or water. For example, U.S.Pat. No. 2,742,375discloses that pigments having improved hydrophobic and organophilicproperties. can be prepared by coating the pigment particles with asmall amount ofa high molecular weight pyridinium chloride. U.S. Pat.No. 3,004,858 discloses that the dispersibility of dry titanium dioxidecan be improved by the use of a non-ionic essentially linear alkyleneoxide polymer. Other benefits associated with improved dispersibilityfrom organic treatment are described in U.S. Pat. Nos. 3,097,219(oxyalkylated carboxylic acid amides), 3,088,837 (pyrollidone) and3,197,425 (reaction product ofa low molecular alkanolamine with a fattyacid having a lipophilic radical of at least carbon atoms).

Other patents dealing with the treatment of pigments with variousorganic agents include U.S. Nos. 3,015,573; 3,147,130; 3,147,131;3,172,772; German Pat. No. 1,166,397; and British Pat. No. 973,463.Since most organic treatment of pigments results in a pigment selectiveto either an oleoresinous or a water vehicle, it is desirable to utilizea treatment that improves a pigments wettability in both oleoresinousand water systems since such treatment would simplify the manufacturingprocess and increase customer utility.

BRIEF SUMMARY OF THE INVENTION It has now been discovered thatpigmentary metal oxides, notably pigmentary titanium dioxide, can beorganically treated to improve their dispersibility in both oleoresinousand water systems, i.e., provide a pigment with both oleophilic andhydrophilic properties. More specifically, and in accordance with thepresent invention, pigmentary inorganic metal oxides are treated with anamine and an organic nitrogen compound having an ionizable hydrogen atomand at least one carbonyl group attached to the nitrogen atom thereof.In particular, the present invention is directed to the treatment ofmetal oxides with an organic amine and ortho-benzosulfimide, morecommonly referred to as saccharin.

DETAILED DESCRIPTION The present invention relates to pigmentary metaloxides of improved dispersibility, dispersion stability and improvedoleophilic and hydrophilic properties and to a method for producing saidpigments. The present invention relates particularly to pigmentary metaloxides having the aforesaid improved properties, notably pigmentarytitanium dioxide, as a consequence of the presence thereon of thereaction product of a proton-donating organic nitrogen compound and anamine.

As used herein, the term metal oxide" is intended to means and includethe so-called metalloid oxides. Examples of metal oxides to which theprocess of the present invention can be applied include the oxides ofaluminum, arsenic, beryllium, boron, cadmium, cobalt, gadolinium,germanium, hafnium, lanthanum, nickel, iron, samarium, scandium,silicon, strontium, tantalum, tellurium, terbium, thorium, thulium, tin,titanium, yttrium, ytterbium, zinc, zirconium, niobium, gallium, an-

timony, and lead. Particularly preferred are the oxides of aluminum,boron, cobalt, nickel, iron, silicon, tin, titanium, zinc, zirconium,antimony and lead.

For the purposes of simplicity and brevity, the present discussion willbe limited to the treatment of titanium dioxide which is, at present,the chief white pigment of commerce.

Pigmentary titanium dioxide is currently produced commercially by twoprincipal processes. One process involves the vapor phase reaction of atitanium halide, i.e., the chloride process. The other process involvesthe acid digestion and hydrolysis of a titaniferous ore, i.e., thesulfate process. The chloride process characteristically involves thevapor phase oxidation of at least one titanium halide, particularly, atitanium tetrahalide, selected from the group consisting of titaniumtetrachloride, titanium tetrabromide and titanium tetraiodide. Titaniumtetrafluoridc is not considered generally to be useful for this process.

Typical vapor phase oxidation and/or hydrolysis processes are describedin U.S. Pat. Nos. 1,885,934 to Mayer; 2,450,156 to Pechukas; 2,502,347to Schaumann; 2,791,490 to Willcox; 2,760,275 to Olson et al.; 2,968,529to Wilson; 3,068,113 to Strain et al.; 3,069,281 to Wilson; British Pat.No. 876,672; and British Pat. No. 726,250.

A vapor phase reaction process may be conducted within or in combinationwith a fluidized bed as disclosed in U.S. Pat. Nos. 2,760,846 toRichmond; 2,856,264 to Dunn, Jr.; 2,964,386 to Evans et al., 3,022,137to Nelson; 3,036,926 to Hughes; 3,073,712 to Wigginton et al., and3,097,923 to Walmsley.

The sulfate process characteristically involves producing a titaniumhydrate by the hydrolysis of a titanium sulfate solution and calcinationof the hydrate to produce titanium dioxide pigment. Typical sulfateprocesses are disclosed in U.S. Pat. Nos. 2,505,344; 2,766,133;2,933,408 and 2,982,613.

The titanium dioxide pigment benefitted by the process described hereinincludes all types and grades of titanium dioxide irrespective of themanner by which it is prepared for the reason that the present processis directed to the treatment of the surface of the pigment. Specificallyincluded are titanium dioxide containing small amounts of alkali and/oralkaline earth metals, e.g., potassium, calcium and magnesium, or theoxides or inorganic salts thereof as conditioning agents; the compoundsof other metals such as antimony, chromium and zinc as brighteners;rutilizing agents such as aluminum or zirconium; particle sizeregulators such as silicon and potassium; and various conventionalhydrous metal oxides, e.g., the hydrous metal oxides of aluminum,titanium, zirconium, silicon, etc., as surface coating agents thatimprove the pigmentary properties of the pigment. The amount of theaforesaid added materials is normally small and usually represents lessthan 25, more usually less than 15, weight percent of the pigment. Theinvention is further usefully applied to titanium dioxide pigmentcontaining extender material such as calcium sulfate, barium sulfate,lithopone, etc.

In accordance with the present process, a pigmentary metal oxide,notably titanium dioxide, is treated with the reaction product of anorganic amine and a proton-donating organic nitrogen compound whereinsaid proton and at least one carbonyl group is attached to the nitrogenatom of said nitrogen compound. The proton, i.e., hydrogen atom, can beattached to the nitrogen atom or in tautomeric equilibrium therewith,i.e.,

The aforesaid treatment produces a pigment with improved oleophilic andhydrophilic properties, i.e., it improves the wettability of the pigmentin both oleoresinous and water systems, and especially improves thedispersibility and dispersion stability of the pigment as measured bythe Hegman texture gage, gloss, tint etficiency and other pigmentperformance tests. By dispersion stability is meant that a pigmenttreated in accordance with the present process exhibits lessdeterioration of dispersion during storage than untreated pigment.

The above-described pigment treatment can be accomplished by anyconvenient method that provides intimate contact of the surface of thepigment with the amine and protondonating organic nitrogen compound.Thus, the treatment can be effected independently of or as an incidentto conventional physical or chemical processing of the pigment, i.e.,prior to, during or subsequent to a stage of said conventionalprocessing.

In one particular embodiment, the pigment can be fluid energy milled inthe presence of one or both of the organic compounds that will bedescribed in more detail hereinafter. In the former case, a secondmilling in the presence of the other organic compound is performed. Byslowly metering the organic compound(s) into the mill simultaneouslywith the introduction of the pigment therein, the organic compound(s)are spread over the surface of the pigment by means of the particlemovement and collisions produced in a fluid energy mill.

in another embodiment, the pigment can be slurried in a suitablesolvent, e.g., water or ethanol, in the presence of one or both of theorganic compounds. By suitable solvent is meant a material that acts asa solvent for both of the organic compounds and is chemically compatiblewith the pigment. In addition, the solvent should be easily removableby, for example, drying the pigment. In a particular embodiment, it iscontemplated slurring the pigment in the presence of the organiccompounds subsequent to the coating of the pigment with hydrous metaloxides. In still another embodiment, pigment is recovered from a slurryby evaporation, spray drying, filtration or other equivalent means anddried in the presence of the organic compounds. In such embodiment, theorganic compounds may be added to the slurry before the pigment isrecovered therefrom, or incorporated with the pigment subsequent torecovery from the slurry.

Further contemplated embodiments of this invention include, not by wayof limitation, physically processing the pigment in the presence of theorganic compounds. Thus, a pigment slurry can be subjected tohydroseparation, milling or otherwise classified in the presence of theorganic compounds.

In a preferred embodiment of this invention, titanium tetrachloride isreacted with oxygen in the vapor phase to produce pigmentary titaniumdioxide. The pigment is recovered, slurried in water, classified byhydroseparation, and coated in aqueous slurry with one or more hydrousmetal oxides, e.g., the hydrous metal oxides of titanium, silicon,aluminum, boron, zinc, zirconium and mixtures thereof. The hydrous oxidecoated pigment is then contacted with the organic agents by the additionof the organic agents to the slurry. The pigment is then recovered fromthe slurry and dried. It is also contemplated that the hydrous oxidecoated pigment be recovered first from the slurry and then organicallytreated.

The practice of the present process is typically carried out attemperatures of less than 300 C., usually from to 250 C. at ambientpressure. Higher temperatures, however, can be used, particularly whenthe pigment slurry is heated and digested under high pressures.Likewise, higher temperatures can be attained when the pigment iscontacted with the organic treating agents in a fluid energy millingoperation (e.g., with superheated steam or an inert gas such asnitrogen) or when the pigment is being heat neutralized with superheatedsteam or NH;,. Likewise, temperatures below 20 C. can be used ifdesired. In any case, the temperature of treatment should be below thetemperature at which the pigment tends to discolor (in the absence ofthe organic treating compounds). Generally, temperatures ofless than 650C., usually below 550 C., do not encounter any significantdiscoloration.

The amount of proton-donating organic nitrogen compound used can varyover a broad range; but, typically will be only that amount required toimprove the dispersibility of the pigment. Typically, from 0.001 to 10.0weight percent, preferably from 0.01 to 3.0 weight percent, ofproton-donating organic nitrogen compound, based on the weight ofpigment treated, is used.

The amount of amine used in combination with the aforesaidproton-donating organic nitrogen compound will also vary as broadly andin the same amounts. Typically, the mole ratio of amine toproton-donating organic nitrogen compound will range from 0.1 to 10.0,more typically from 0.1 to 5.0, and preferably from 0.1 to 1.0.Generally, the total amount of amine and proton-donating organicnitrogen compound, i.e., the reaction product, used varies from 0.002 to10 weight percent, preferably from 0.02 to 5 weight percent, based onthe amount of pigment treated.

The proton-donating organic nitrogen compounds useful in the presentprocess are organic compounds containing an imido group adjacent to atleast one carbonyl group Preferably, the two covalent bonds of the imidogroup are satisfied by a carbonyl group and an electron withdrawinggroup. Most preferably, the electron withdrawing group is anothercarbonyl group. Thus, the proton-donating organic nitrogen compounds ofthe present process contain the grouping and preferably contain thegrouping wherein A is an electron withdrawing group such as a carbonylgroup, i.e.,

Electron withdrawing groups or atoms are atoms or groups of atoms whichhave the ability to attract electrons. This property is commonlyreferred to as electronegativity which has been defined as the power ofa chemically bonded atom or group to attract electrons to itself. Thisconcept is used to designate the relative electropositive orelectronegative character of an element or group as it appears in agiven state of chemical combination. The concept of electronegativityand electron withdrawing groups is well known. Atoms or groups typicallycharacterized as being electronegative or electron withdrawing include:unsaturated linkages, e.g., unsaturated carbon-carbon linkages ,i =s.:;s

(particularly allylic unsaturation) and imino groups 7 a? PEEL-HE nitro(O N-) and nitroso (ON-) groups; aryl, e.g., phenyl groups; sulfonyl andsulfmyl (sulfoxide) groups; nitrile (-CN) groups; phospho (O P-) andphosphoroso (OP) groups; mono-, diand trihalogen containing carbonatoms; and ring halogen substituted aryls, e.g., chlorophenyl. The termhalogen is meant to include fluorine, chlorine, bromine and iodine.

The utility of the aforementioned proton-donating organic nitrogencompounds is based on the ability of the imido nitrogen atom to lose ordonate its proton which ability is a function of the presence of theelectron withdrawing group(s) adjacent to the imido group. In the Lewisconcept of acids and bases, the proton-donating organic nitrogencompound is an acid, i.e., an electron acceptor or proton donor. Thus,any nitrogen compound containing the structure has the ability to donatethe proton (H atoms) attached to the imido nitrogen atom and therebyacts as a Lewis acid because of the presence of the adjacent carbonylgroup. The remainder of the molecule has little effect on the compoundsproton-donating ability and, therefore, any nitrogen compound containingthe aforesaid structure can be used in the present process. The presenceof an additional adjacent electron withdrawing group, i.e.,

II I ll makes the nitrogen compound a stronger Lewis acid, i.e., theproton is more mobile. Thus, electrons associated with the nitrogen atomof the imido group are drawn away from the hydrogen of that grouppermitting the hydrogen to be mobile (lost) and drawn to a protonaccepting molecule, a Lewis base, which in the present process is anamine.

The proton-donating organic nitrogen compounds of the present processcan be either open chain or cyclic (including bicyclic) in character.They can be represented by the following general formulas:

T if wherein R, R and R" can be saturated hydrocarbons, unsaturatedhydrocarbons, halogenated hydrocarbons, hydroxy and carbonyl substitutedhydrocarbons, aryl, e.g., phenyl groups, and heteroatom containinghydrocarbons. Common heteroatoms include phosphorous, sulfur, oxygen ornitrogen. Such hydrocarbons can be linked to the imido nitrogen atoms orcarbonyl carbon atom by a carbon atom, oxygen atom, nitrogen atom,sulfur atom or carbon atom of a carbonyl group. R and R" may not behydrogen, hydroxyl, or amino and R may not be hydroxyl since such groupsdestroy the proton-donating ability of the imido nitrogen.

In the above formula I, R and R can each be selected from the groupconsisting of C -C preferably C,C alkyl, C -C preferably C -C alkenyl, CC preferably C -C alkynyl, C -C aryl, C -C cycloalkyl, C -Ccycloalkenyl, C C arylalkyl, C -C alkylaryl; C -C alkenylaryl andarylalkenyl; C -C arylalkynyl; and C -C heterocyclic radicals. In theabove formula II, R represents the remaining portion of the heterocycliccompound depicted and typically represents from three to six atoms whichcan be selected from the group consisting of one to six carbon atoms,one to three nitrogen atoms, one to two carbonyl groups and mixturesthereof.

Most preferably, the proton-donating organic nitrogen compounds of thepresent process are depicted by the following general formulas:

III

wherein A is an electron withdrawing group, as described above, R and Rare the same as described above and R represents from two to six atomswhich can be selected from the group'consisting of one to six carbonatoms, one to three nitrogen atoms, a carbonyl group and mixturesthereof.

When R and R are hydrocarbon radicals or heteroatom containinghydrocarbon radicals, it is preferred that each should not exceed 24carbon atoms, more preferably less than 12 carbon atoms, so thatcompounds represented by formulas I and III above do not exceed a totalof 49 carbon atoms, and preferably are less than 25 carbon atoms.

Typical alkyl radicals that can be substituted for R and R in the aboveformulas include: methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl,decyl, hendecyl, dodecyl, octadecyl, 2-ethylhexyl, 2-ethyloctadecyl,2-nonylhendecyl, and 2-octyldodecyl. Alkenyl radicals that can be usedinclude: l-ethenyl, 3-butenyl, 4-hexenyl, G-heptenyl, 8-nonenyl,IO-hendecenyl, l ldodecenyl, 17-octadecenyl, l9-eicosenyl,l-methyl-Z-propenyl, 2-ethyl-l2-tridecenyl, l-heptenyl-9-decenyl,Z-methyl-l 8- nonadecenyl, 1,3-pentadienyl, 2-dimethyl-5-hexenyl and 3-chloro-l-butenyl.

Typical alkynyl radicals that can be substituted for R and R in theabove formulas include: l-ethynyl, 4-pentynyl, S-hexynyl, 9-decynyl,l2-tridecynyl, l5-hexadecynyl, l9-eicosynyl, l-methyl-4-pentynyl,2,2,4-trimethyl-5-hexynyl, and l-ethyll7-octadecynyl. Typical cycloalkyland cycloalkenyl radicals include: cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, 3- cyclohexenyl and cyclopentyl.

Typical aryl radicals that can be substituted for R, R and R in theabove formulas include: phenyl, p-terphenyl, quinonyl, metaphenylene andnaphthyl. Typical arylalkyl and alkylaryl radicals include: benzyl,meta-tolyl, meta-xylyl, Z-phenylpropyl, indanyl, and para-cyclohexylphenyl. Typical arylalkenyl or alkenylaryl radicals include:beta-styryl, meta-isopropenyl phenyl and para-l-cyclohexenyl phenyl.Typical arylalkynyl or alkynylaryl radicals that can be used include:phenylethynyl and meta-ethynyl phenyl.

Typical heterocyclic radicals that can be used include: benzofuryl,furyl and benzopyranyl. Typical contemplated radicals contailing atomsother than carbon and hydrogen include, but not by way of limitation,the thioalkyls, alkoxys such as phenoxy, benzoyl, acetyl, naphthoyl,salicyl, phenylcarbamido, phthalyl, anthranilo and benzohydryl.

Typical groups of proton-donating organic nitrogen compounds depictableby the aforesaid formulas I, II, III or IV include, not by way oflimitation, derivatives of urea, urcides, allophanates, substitutedamides, substituted imides, the triazine triones, triazine diones,diazine diones and diazine triones.

Representative examples of organic proton-donating organic nitrogencompounds within the scope of formula I include: C I-I NHCOCI-I CH OC HNI-ICOCH (p-methoxyacetanilide), CH CONI-IC H SO Na 2H O (1,3), CH CONI-IC I-LOC H (acetphenetidide including orth o, meta and para), CH CH,NHCOCI-I (acettoluidide inauding ortho, meta and para),o-hydroxyacetanilide, n-acetyl naphthylamide, including alpha and beta,(CH C =NNH- CONI-I (acetone semicarbazone), dimethyl hydantoin, acetylbiuret, ethyl allophanate, n-benzoyl hydroxyl amine, C I-I NH- COC H(benzanilide), benznaphthalide, phenyl urea, bromoacetanilide (ortho,meta and para), n-acetylaminophenol (ortho, meta and para), CH CONI-ICILOH (3- acetaminophenol), bromo and chloro acetoacetanilide (ortho,meta and para), bromo and chloro acettoluidide (ortho, meta and para),butyric anilide, carbazide, chloro acetamide,

chloro acetanilide (ortho, meta and para), chlorobenzamide (ortho, metaand para), alpha-citral semicarbozone, 3- semicarbazidobenzamide, cyanoacetamide, cyano acetanilide (ortho, meta and para) diacetimide,C,N-diacetyl paminophenol, diacetyl benzidine, N,N-diacetylphenylenediamine (ortho and para), N,N -dibenzoyl ethylenediamine,dibromoacetamide, dichloroacetamide, diethyl ketone semicarbazone,S-acetamido 1,3-dimethyl benzene, 5,5-diphenyl hydantoin, l,l-diphenylsemicarbazide, 2,4-diphenyl semicarbazide, symmetrical and unsymmetricaldiphenyl urea, phthalimide ethyl allophanate, N-ethyl-N'- phenyl urea,isovaleric anilide, pyrimidone, 2,4,6-trioxypyrimidine (barbituricacid), tribromoacetamide, ortho, meta and para tolyl urea, nitro urea,nitro urethane, para, ortho and meta nitro benzamide,4-nitro-2-acetnaphthalide, N-acetylurea, veronal, ethylallophanate,decylallophanate, octadecylallophanate, the imide of chlorendicanhydride and ortho-benzosulfimide (saccharin).

Utilized in conjunction with the aforesaid proton-donating organicnitrogen compound for treating the pigment is an amine. In the Lewisacid-base concept, the amine is an electron donor or proton acceptorbecause ofthe unshared pair of electrons on the nitrogen atom of theamine. Since all amines have this characteristic, any amine capable ofaccepting a proton from the proton-donating organic nitrogen compoundcan be used in the present process.

Amines which are particularly contemplated for use in the processdescribed herein include: C C iso and normal primary, secondary andtertiary amines, which include by definition the alkylmonoamines,alkyldiamines, alkyltriamines, alkynylmonoamines, alkynyldiamines,alkynyltriamines, alkenylmonoamines, alkenyldiamines, alkenyltriamines,arylmonoamines, aryldiamines, aryltriamines, arylalkyldiamines andcyclicalkylamines. Preferred are tertiary amines of from one to 10carbon atoms.

Representative examples of such amines include, not by way oflimitation, cyclopentylamine, cyclohexylamine, methylamine, ethylamine,n-propylamine, isopropylamine, nbutylamine, isobutylamine, n-amylamine,isoamylamine, nhexylarnine, iso-hexylamine, laurylamine, hexadecylamine,stearylamine, dimethylamine, diethylamine, di-npropylamine,di-n-butylamine, di-n-amylamine, di-n-hexylamine, dilaurylamine,dihexadecylamine, trimethylamine, triethylamine, tri-n-propylamine,tri-n-butylamine, tri-namylamine, tri-n-hexylamine, trioctylamine,trilaurylamine,

trihexadecylamine, dodecylamine, octadecylamine, ethyleneamine,ethylenediamine, triethyleneamine, diethylenetriamine,trimethylenediamine,

tetramethylenediamine, pentamethylenediamine, hexamethylenediamine,l,6-hexanediamine, N- cocotrimethylenediamine, alkylol amines includingmonoisopropanolamine, methylisopropanolamine, phenmonobutanolamine,monoethanolamine, monopropanolamine, beta-phenylethylamine,dibutanolamine, methylethanolamine, ethylbutanolamine,monomethanolamine, dimethanolamine, trimethanolamine, diethanolamine,dipropanolamine, acetylisobutylamine, dibeta-phenylethylamine,diethylhexanolamine, triethanolamine, tripropanolamine,acetyldiisopropylamine, N-nitrosodimethylamine,N-soyatrimethylenediamine, N-tallowtrimethylenediamine,bis-2hydroxyethyl soyabean amine,

ylethanolamine,

morpholine, N-methyl morpholine, pyridine, Z-methyl pyridine, 4-methylpyridine, piperidine, 4-picoline, melamine, benzylamine, triphenylamine,tribenzylamine, o-phenylenediamine, p-phenylenediamine andm-phenylenediamine.

In selecting the particular proton-donating organic nitrogen compoundand organic amine to be used in the practice ofthe present process, therelative strength, i.e., acidity (proton donor) and basicity (protonacceptor), of each is taken into consideration. Thus, a weakly acidicproton-donating organic nitrogen compound should be used with a stronglybasic amine and vice versa to insure that a reaction, i.e., protontransfer, occurs between the two treating agents. The use ofa stronglyacidic proton donator and strongly basic amine is preferred. Thedetermination of the relative acidity or basicity of the aforementionedrespective compounds is performed by examination of the chemicalstructure of the particular compound, i.e., by examination of theelectronic configurations around the nitrogen atoms of the respectivetreating agents. Such determinations are well known in the field ofchemistry and need not be discussed herein.

A practical method for determining if a reaction (proton transfer)occurs between a particular proton-donating organic nitrogen compoundand amine is to mix the two agents and see if there is a change in thewater solubility of the mixture. The water solubility can increase ordecrease; however, the change in solubility indicates that a reactionhas occurred.

Although not intending to be bound by any particular theory, it is beleved that the improved dispersibility of pigments treated in accordancewith the present process in oleoresinous vehicles is produced by thepresence of the organic portion of the reaction product of theproton-donating nitrogen compound and amine on the surface of thepigment. Similarly, the improved dispersibility in water of suchpigments, i.e., the hydrophilic character, is produced by the ioniccharacter of the reaction product as a result of the proton transferdiscussed above.

In treating pigment with the reaction product of the protondonatingorganic nitrogen compound and amine, either agent can be addedseparately to the pigment or both can be added simultaneously.Preferably, the proton-donating compound is added to the surface of thepigment first, the amine added thereafter and the reaction between thetwo permitted to occur on the surface of the pigment. In anotherembodiment, the two reagents can be premixed and the mixture applied tothe surface of the pigment. In still another embodiment, a commonsolvent for both the proton-donating compound and amine can be used toprovide a premixture or to aid in the application of each agent to thepigment surface. When a solvent is used, care should be exercised in itsselection so that it is not of the type which will interfere or hinderthe reaction between the treating agents, hinder the dispersion of thepigment and be difficult to remove from the surface of the pigment.Water and ethanol are exemplary of two solvents that can be used.

The practice of the present process improves the pigmentary propertiesof the pigment treated. For example, titanium dioxide pigment treated inaccordance with this invention characteristically has improved tintingstrength, tint efficiency, tint tone, wetting and dispersioncharacteristics. The tinting strength and tint tone of pigment can bedetermined by A.S.T.M. Method D332-26, 1949 Book of A.S.T.M. Slandards,Part IV, page 31, published by American Society for Testing Materials,Philadelphia 3, Pennsylvania. The tint effciency, as used herein, refersto the reflectometry method disclosed on pages 704 to 7 l 5, Volume 34of the Journal of Pain! Technology and Engineering, (Official Digest,July, 1962), now A.S.T.M. Test Method D-2745-687. The wettingcharacteristics of a pigment refer to the ease of incorporation of thepigment into paint vehicles or vehicle systems. Dispersion can bedefined as the ability of a pigment to distribute in a dissimilarsubstance, particularly a paint vehicle and usually a non-aqueousorganic vehicle. In the pigment art, dispersion is frequently referredto as the fineness of grind of pigment as measured by the Hegman gage,(A.S.T.M. Test Method D12l0-D).

Since the present process is generally applied to pigments thattypically produce a high Hegman dispersion rating, a test was developedthat would discriminate small but significant differences in dispersion.In this test, referred to herein as the Low Shear Dispersion Test, ahigh quality commercial titanium dioxide pigment that normally yields adispersion rating of 7 /2 Hegman in a standard dispersion test isprocessed to yield from a 5 to 5 /2 Hegman rating. In this manner,improvements in dispersion by the application of the present process canbe readily detected. In this test, increases of from A ofa unit on theHegman scale are significant. Increases of one unit represent a highlysignificant improvement.

The Low Shear Dispersion Test used to evaluate dispersion in theexamples presented hereinafter was performed in the following manner.Into a mixing container were weighed 1 15 grams of alkali refinedlinseed oil 1/ (1/ PPG F. L. Golden Varnish Oil VD18; Viscosity -A minusor less; Acid Number 0.5 Max.), 90 grams of mineral spirits 2/ (2/Distillation range 315 to 390 F.), and 135 grams of pigment to betested. The container was placed on a Hamilton Beach Blender 3/ (3/Model No. 936; Impellor used is the clover-leaf type permanentlyattached to shaft of Model No. 960 Hamilton Beach Blender. Diameter ofimpeller is 1% inch and has a l-inch clearance from bottom of mixingcontainer which has a height of 7 inches, a top inside diameter of 33/16 inches which tapers to a 2 /2 inch diameter at the bottom.) and thesample milled for minutes at the speed setting marked Medium on theblender. After milling, a portion of the sample was transferred to a 50ml. tri-pour beaker, stirred there about 1 minute with a glass stirringrod, and the sample paste poured promptly onto the upper channel sectionof the Hegman gage. The sample paste was then drawn down with avertically held drawbar at a uniform rate and the gage read inaccordance with A.S.T.M. Method D-l 2 10-64. The gage was read within 20seconds of draw down to avoid solvent evaporation effects. The readingrepresents the point on the scale adjacent the groove above which thereare substantially no particles appearing above the surface of the film.Such reading has been referred to as the secondary grind.

The present process is more particularly described in the followingexamples which are intended as illustrative only since numerousmodifications and variations therein will be apparent to those skilledin the art.

EXAMPLE I Titanium dioxide prepared by oxidation of titaniumtetrachloride with oxygen at about 1,000 C. in the presence of aluminumchloride and silicon tetrachloride (reactor discharge oil absorption offrom about 16 to 17) and containing a surface coating of hydrous titaniaand hydrous alumina was organically treated by intimately mixing asample thereof in a beaker with a sufficient amount of an aqueoussolution containing triethanolamine and ortho-benzosulfimide which werepresent in a mole ratio of 1:1.1 (amine to imide), to place 0.2 weightpercent of the amine-imide reaction product (basis TiO on the pigment.The treated pigment was recovered and dried overnight in an oven atabout 90 C. After drying, the pigment was fluid energy milled twice at250 lbs. pressure at a feed rate of 150 grams/minute.

A portion of the dried recovered pigment is gradually mixed with analkali refined linseed oil vehicle in a Cowles Dissolver (LaboratoryModel). The Cowles Dissolver is operated at a blade speed of 2,000linear feet per minute until all of the pigment has been incorporatedinto the vehicle. The blade speed is then increased rapidly to 2,550linear feet per minute. After 10 minutes, the dissolved pigment isremoved from the Cowles Dissolver. The fineness of grind is thendetermined for the pigment using A.S.T.M. Method D-l2l0-64, Part 21,Jan., 1965. The pigment has a fineness of grind rating of5 Hegman.

For comparison, a portion of the above hydrous oxide coated pigmentwhich was not organically treated with the triethanolamine-imidesolution was processed in the Cowles Dissolver, as above. The finenessof grind for the untreated pigment was 3%: Hegman.

EXAMPLE ll ness of grind rating of 4% He man.

EXA PLE Ill Portions of the hydrous oxide coated titanium dioxidepigment of Example I was treated separately with 0.2 weight percent(basis TiO of ortho-benzosulfimide, triethanolamine and melamine forcomparison purposes. The aforementioned treated pigments were found tohave fineness of grind ratings of3 3% and 4% Hegman.

The data of Examples l I]! show that the combined use oforthobenzosulfimide (a proton-donating organic nitrogen compound) andtriethanolamine or melamine (proton-accepting organic amines) improvedthe dispersibility of pigmentary titanium dioxide over the use alone ofthe proton-donating compounds or of the organic amines as evidenced bythe above-described Low Shear Dispersion Test.

While there are above-described a number of specific embodiments of thepresent invention, especially in connection with pigmentary titaniumdioxide, it is obviously possible to produce other embodiments andvarious equivalent modifications thereof without departing from thespirit of the inventron.

Having set forth the general nature and specific embodiments of thepresent invention, the scope thereof is now particularly pointed out inthe appended claims.

I claim:

1. A process for treating pigmentary metal oxide, which comprisescontacting said metal oxide with from 0.002 to 10 weight percent, basedon metal oxide, of the reaction product of (a) an organic amine selectedfrom the group consisting of C C primary, secondary and tertiary amines,and (b) ortho-benzosulfimide.

2. A process according to claim 1 wherein the pigmentary metal oxide istitanium dioxide.

3. A process according to claim 1 wherein said organic amine is selectedfrom the group consisting of triethanolamine and melamine.

4. A process for treating pigmentary titanium dioxide which comprisescontacting said pigment with from 0.002 to l0 weight percent based ontitanium dioxide, of the reaction product of ortho-benzosulfimide and anorganic amine selected from the group consisting of triethanolamine andmelamine.

5. A process according to claim 4 wherein the pigmentary titaniumdioxide treated has a hydrous metal oxide coating.

6. The process according to claim 4 wherein the pigment is contactedfirst with the ortho-benzosulfimide and then with the organic amine.

7. Pigmentary metal oxide having on its surface from 0.002 to 10 weightpercent, based on metal oxide, of the reaction product of (a) an organicamine selected from the group consisting of C C primary, secondary andtertiary amines, and (b) ortho-benzosulfimide.

8. Pigmentary metal oxide according to claim 7 wherein the oxide istitanium dioxide.

9. Pigmentary titanium dioxide according to claim 8 wherein the organicamine is selected from the group consisting of triethanolamine andmelamine.

2. A process according to claim 1 wherein the pigmentary metal oxide istitanium dioxide.
 3. A process according to claim 1 wherein said organicamine is selected from the group consisting of triethanolamine andmelamine.
 4. A process for treating pigmentary titanium dioxide whichcomprises contacting said pigment with from 0.002 to 10 weight percentbased on titanium dioxide, of the reaction product ofortho-benzosulfimide and an organic amine selected from the groupconsisting of triethanolamine and melamine.
 5. A process according toclaim 4 wherein the pigmentary titanium dioxide treated has a hydrousmetal oxide coating.
 6. The process according to claim 4 wherein thepigment is contacted first with the ortho-benzosulfimide and then withthe organic amine.
 7. Pigmentary metal oxide having on its surface from0.002 to 10 weight percent, based on metal oxide, of the reactionproduct of (a) an organic amine selected from the group consisting of C1-C20 primary, secondary and tertiary amines, and (b)ortho-benzosulfimide.
 8. Pigmentary metal oxide according to claim 7wherein the oxide is titanium dioxide.
 9. Pigmentary titanium dioxideaccording to claim 8 wherein the organic amine is selected from thegroup consisting of triethanolamine and melamine.